Chemo- and stereoselectivity in titanium-mediated regioselective ring-opening reaction of epoxides at the more substituted carbon
作者:Tetsuaki Tanaka、Kei Hiramatsu、Yasutaka Kobayashi、Hiroaki Ohno
DOI:10.1016/j.tet.2005.05.006
日期:2005.7
Chemo- and stereoselectivity in the ring-opening reaction of epoxides with a reagent prepared from allylmagnesium halide and chlorotitanium triphenoxide is described. It has been proven that the allylating reagent can also be used for the reaction of epoxides bearing a tert-butyl ester, amide, or acetal moiety, and that the epoxide cleavage regioselectively takes place at the more substituted carbon
描述了环氧化物与由烯丙基卤化镁和三氧化氯钛制备的试剂在开环反应中的化学和立体选择性。已证明烯丙基化试剂也可用于带有叔丁酯,酰胺或乙缩醛部分的环氧化物的反应,并且在所有情况下,环氧化物的裂解均在更高取代的碳上进行。有趣的是,尽管无环2,2,3-三烷基环氧化物或3,3-二取代的2,3-环氧醇衍生物与烯丙基钛试剂的反应产生的烯丙基化产物几乎为1:1的非对映混合物,但其开环反应为2-取代的2,3-环氧醇衍生物立体定向地通过抗途径。后者反应对于季碳中心的不对称结构非常有用。